Referring to FIG. 1, an image projector according to prior art comprises a light source 360 to provide light B0, and a polarizing beam splitter 260 to form a polarized illuminating light B2 by reflecting light B0. The illuminating light B2 impinges on the pixels P1, P2, P3 of a reflective micro display 200. Depending on the state of the pixels P1, P2, P3, light B3 reflected from each pixel P1, P2, P3 may have the same polarization state as the illuminating light B2, or its polarization may be changed. Only light whose polarization state has been changed passes through the splitter 260 to the imaging optics 300. The imaging optics 300 focuses or collimates light B3 so as to form light B5. The light B5 may be directed to a screen in order to project an image IMG.
The polarizing beam splitter 260 is typically an inclined plate or a polarizing cube beam splitter. The dimension of these components in the direction SZ is rather large. Thus, it may be difficult to incorporate a prior art image projector e.g. into a slim mobile phone.
U.S. Pat. No. 6,814,442 discloses a virtual display device comprising a prism, which is combined with polarizers.